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https://issues.apache.org/jira/browse/HDFS-5891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13899794#comment-13899794
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Brandon Li commented on HDFS-5891:
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I've committed the patch. Thank you, Haohui and Jing.
> webhdfs should not try connecting the DN during redirection
> -----------------------------------------------------------
>
> Key: HDFS-5891
> URL: https://issues.apache.org/jira/browse/HDFS-5891
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode, webhdfs
> Reporter: Haohui Mai
> Assignee: Haohui Mai
> Fix For: 2.4.0
>
> Attachments: HDFS-5891.000.patch, HDFS-5891.001.patch
>
>
> When the webhdfs server in NN serves an {{OPEN}} request, the NN will
> eventually redirect the request to a DN. The current implementation intends
> to choose the active DNs. The code always connects to the DN in a
> deterministic order to see whether it is active during redirection.
> Although it reduces the chance of the client from connecting to a failed DN,
> this is problematic because:
> # It has no guarantees that the client can connect to that DN even if the NN
> can connect to it.
> # It requires an additional network round-trip for every {{OPEN}} /
> {{CREATE}} request.
> This jira proposes that the NN should choose the DN based on the information
> of the data node manager.
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